1. Field of the Invention
The present invention relates to an image taking apparatus that captures object light and produces image data representing an object image.
2. Description of the Related Art
One example of such image taking apparatus is a digital camera that captures object light with a solid-state imaging device and produces image data representing the object image. Such a digital camera has been popular for quite a few years. However, the charge coupled device (CCD), which is commonly used in the digital camera as the solid-state imaging device for capturing object light, has a disadvantage that the dynamic range for the quantity of object light is narrow compared with the silver-salt film. That is, if the quantity of object light exceeds the upper limit of the dynamic range for the quantity of light, the CCD, which outputs signals corresponding to the quantity of object light, becomes saturated and can output only fixed signals. On the other hand, the silver-salt film captures object light by changing the photosensitivity in accordance with the quantity of the object light. The silver-salt film also has a dynamic range for the quantity of light and becomes saturated if the object light is too intense and exceeds the upper limit of the dynamic range. However, the upper limit of the dynamic range of the CCD is lower than that of the silver-salt film. As a result, a picture printed based on the image data produced by the digital camera with such a CCD suffers the so-called whiteout in a bright part of the object image or the so-called blackout in a dark part of the object image. For example, a picture of a clear sky with clouds and a person in the shade of a tree may be poor in quality due to whiteout in the part of the clouds or blackout in the part of the person.
In recent years, there has been developed a technique as described below to overcome the above drawback of the CCD. According to this technique, one CCD is composed of an array of composite pixels, each of which is a pair of a primary pixel of high sensitivity and a secondary pixel of wide dynamic range. In the following description, the CCD composed of an array of such composite pixels will be referred to as a composite CCD, the part of the composite CCD which is composed of an array of such primary pixels will be referred to as a primary CCD section, and the part of the composite CCD which is composed of an array of such secondary pixels will be referred to as a secondary CCD section. According to this technique, dark object light of a small quantity of light is captured by the primary CCD section composed of primary pixels of high sensitivity. And bright light of a large quantity of light, which may make the primary CCD section saturated, is captured by the secondary CCD section composed of secondary pixels of wide dynamic range. The image data representing the object image is obtained by synthesizing the output signals from the primary CCD section and the secondary CCD section. In this way, the whiteout and the blackout described above can be prevented.
In a photo printing shop, when image data produced by the digital camera is received from a user asking for printing, the printer for producing pictures from the image data typically automatically performs an image correction processing, such as gradation correction, tone correction and white balance correction, on the image data. In the printer, data determined to represent an excessively bright image is regarded as a noise or the like and smoothed via the image correction processing. As a result, if the user asks for printing of a picture based on the image data representing an object image of a scene of a wide dynamic range produced by the high-performance digital camera with the composite CCD, the image data representing delicate gradations or the like of the bright object light captured by the composite CCD may be smoothed by the involuntary image correction processing, and the printed picture may be poor in quality due to whiteout or the like, as is conventional. That is, even if rich image data representing an object image of a scene of a wide dynamic range is obtained by the high-performance digital camera described above, part of the rich data may be wasted in printing.
There has been developed a printer used in photo printing shops that can appropriately inhibit an image correction processing, such as gradation correction, tone correction and white balance correction, of image data not to interfere with the intention of the user if the user has taken pictures by adjusting the shutter speed, the aperture or the like according to a particular intention.
As an example of the digital camera designed for such a printer, there has been proposed a digital camera that is provided with a typical CCD, has a user-selectable shooting mode, such as a manual mode and an exposure correction mode, in which the user can adjust the shutter speed or the aperture during photographing, and has a function of adding, to the image data obtained in such a shooting mode, correction inhibiting information that indicates that an image correction processing, such as gradation correction, tone correction and white balance correction, of the image data (for example, see Japanese Patent Laid-Open No. 2002-156711 (p. 4-9, FIG. 5 )) is inhibited. For the image data with the correction inhibiting information obtained in such a digital camera, the printer inhibits the image correction processing of the image data in accordance with the correction inhibiting information.
It seems that the disadvantage of the printing can be avoided by applying the invention disclosed in Japanese Patent Laid-Open No. 2002-156711 to the digital camera with the composite CCD.
However, the digital camera disclosed in Japanese Patent Laid-Open No. 2002-156711 requires the user to perform some intentional manipulation of the digital camera, such as switching of the shooting mode, in order for the printer to inhibit an image correction processing, such as gradation correction, tone correction and white balance correction, of the image data obtained by photographing. Thus, it is difficult to apply the technique disclosed in Japanese Patent Laid-Open No. 2002-156711 to the high-performance digital camera that produces high-volume image data representing an image of a wide dynamic range regardless of the intention of the user.
In addition, the image processing of the high-volume image data obtained in the high-performance digital camera, which is performed by the printer, is not always desired to be inhibited. For example, if available image data disproportionately exists in a certain part of the dynamic range due to poor photographing, it is desirable that the image data obtained in the digital camera is effectively used by selecting the available data or performing an appropriate correction processing to make use of the available data. However, the technique disclosed in Japanese Patent Laid-Open No. 2002-156711 cannot handle such a situation.
While problems have been described by taking the digital camera as an example, these problems concern not only the digital camera but also other image taking apparatus that capture object light and produce image data representing the object image.